Resistance to pests and pathogens is increasingly becoming a major challenge in agriculture and horticulture worldwide. Resistance occurs when a pest or disease builds up a tolerance and becomes resistant to a specific chemical, rendering the product ineffective.
According to Irene de Bruijn, Team Lead Microbial Profiling at Koppert, resistance can occur when a grower repeatedly uses a product with the same mechanism of action. A mechanism of action is the way a crop protection product controls a pest or disease. For example, if a crop protection product blocks only one characteristic of the pest, there is an increased risk of resistance development.
Resistance to pests and diseases: what happens?
"The individual pests and diseases themselves do not become resistant, but the population adapts through small changes in their DNA. For example, when pests resistant to chemicals reproduce, they pass on their genetic makeup to their offspring, and their offspring in turn are more likely to be resistant to the chemical," Irene explains. "We see the most resistance in crops grown in monoculture, where crops are grown in large numbers with a high population of pests and diseases. The faster the life cycle of the pest or disease, the higher the likelihood of resistance."
Why is organic crop protection different?
Biological crop protection is a natural form of pest and disease control, and the very low likelihood of resistance is one of the main advantages of including biological crop protection in a comprehensive IPM strategy. Many biological crop protection products often have multiple mechanisms of action. For example, fungi can develop into pest organisms and suffocate them. Beneficial insects and mites can prey on different life stages of a pest and can actively seek them out in hard-to-reach places. Each time a grower uses a different mode of action, the pest has to develop a new way to counteract crop protection.
A good example is Trianum (Trichoderma harzianum), which has multiple modes of action. Trianum defends the plant against soilborne pathogens by forming a barrier around the roots and attacking pathogens through mycoparasitism. It also improves the root system by forming more root hairs so that water and nutrients can be better absorbed. This leads to a stronger and more uniform crop and better yields. This effect is stronger when the plant is under stress and/or grown under less than optimal conditions. Trianum also strengthens the defense mechanisms of above-ground plant parts, called induced systemic resistance (ISR), and produces compounds that break down the cell walls of fungal diseases.
Future role of biological crop protection
Irene stresses that it is important for a grower to include multiple modes of action in a resistance strategy. Biological crop protection should be part of a comprehensive IPM strategy. Growers need to understand their crops and associated pests and diseases well. "A good application strategy is very important for effective biological crop protection. Growers need to know how and when to apply agents, at the right time and at the right dosage. Preventive measures such as crop rotation and good hygiene also contribute to effective crop protection within IPM. Looking at the future role of organic crop protection, especially in light of growing concerns about pesticide resistance in agriculture and horticulture, Irene stresses that it is important for the organic crop protection industry to learn from the development of resistance to chemicals. IPM is very important, and we need to develop a good strategy and ensure that we continue to provide biologicals based on multiple mechanisms of action."
"Combine different strategies and compounds, including micro and macro agents that target the same pest but have different mechanisms of action. This will ultimately strengthen control and reduce resistance," concludes Irene.
For more information:
Koppert
Veilingweg 14
2651 BE Berkel en Rodenrijs, the Netherlands
Tel: +31 (0) 10 514 04 44
[email protected]
www.koppert.nl